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Why do some people kill themselves?

FOR a few months in late 2006 and early 2007, the woman who called herself kristi4 was one of the best-known members of the pro-anorexia community. As the administrator of a blog on LiveJournal.com, she dispensed advice, encouraged others and wrote candidly about her own struggles. Then, late one Friday night, after a series of entries describing what she was planning to do, kristi4 killed herself with an overdose of prescription sleeping pills, muscle relaxants and painkillers.

Her death was just one tragic data point in one of the most striking statistics in all of psychology. It has long been known that anorexia has the highest death rate of any mental illness&colon; one out of every five people with anorexia eventually die of causes related to the disease. What has only now been recognised, however, is that a huge number of those deaths are from suicide rather than starvation. Someone who develops anorexia is 50 to 60 times more likely to kill themselves than people in the general population. No other group has a suicide rate anywhere near as high (Archives of General Psychiatry, vol 60, p 179).

Recently, psychologists have tried to explain why anorexia and suicide are so intimately connected, something which is helping to answer the wider question of why anyone would commit suicide. If this explanation holds up, it will give psychiatrists a new tool for screening patients and determining which of them are most likely to kill themselves, perhaps saving lives.

Suicide has always been a conundrum for psychologists and other researchers interested in human behaviour. Self-preservation is one of the …